CHAPTER 1
INTRODUCTION
1.1 ELECTRICAL DISCHARGE MACHINING (EDM)
The phenomenon of erosion of metals by electric spark was first noticed by Joseph Priestily in 1878 but this was not used for machining of metals until 1930s. Controlled machining of metals by electric sparks was first done by Lazarenko in Russia in 1944 [2].
One of the most widely used Non-Conventional Machining process in industry is Electrical Discharge Machining (EDM). Electric Discharge Machining is a non- traditional concept which is based on the principle of removing material by means of repeated electrical discharges between the tool termed as electrode and the work piece in the presence of a dielectric fluid [3]. Electrical Discharge Machining (EDM) uses thermal energy to achieve a high-precision metal removal process from a fine, accurately controlled electrical discharge. The electrode is moved towards the work piece until the gap is small enough so that the impressed voltage is great enough to ionize the dielectric [1]. Short duration discharges are generated in a liquid dielectric gap, which separates tool and work piece. The material is removed with the erosive effect of the electrical discharges from tool and work piece. EDM does not make direct contact between the electrode and the work piece thus it can eliminate mechanical stresses, chatter and vibration problems during machining [3, 4].
EDM is commonly used for machining very hard and tough materials such as tool steels and carbides and for finishing parts for aerospace, automotive industry and surgical components. It is also used to produce complex shapes and small diameter holes, which are difficult or impossible to machine using conventional methods. Since EDM uses an electric discharge ...
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...essing because of the abilities to provide accurate, cost-effective and flexible products.
1.4.1 Advantages of WEDM Process:
• As continuously travelling wire is used as the negative electrode, so electrode fabrication is not required as in EDM.
• There is no direct contact between the work piece and the wire, eliminating the mechanical stresses during machining.
• WEDM process can be applied to all electrically conducting metals and alloys irrespective of their melting points, hardness, toughness or brittleness.
• Users can run their work pieces over night or over the weekend unattended.
1.4.2 Disadvantages of WEDM Process:
• High capital cost is required for WEDM process
• There is a problem regarding the formation of recast layer
• WEDM process exhibits very slow cutting rate
• It is not applicable to very large work piece
However, metals can be quite hard to cut or shape into a desirable piece, requiring application of extreme forces. Depending on the project,
“The Industrial Revolution was another of those extraordinary jumps forward in the story of civilization” (Stephen Gardiner). One of the major parts of the industrial process has to do with metal production. Welding has been incorporated into the framework of metalworking. Welding dates back to the middle ages where forge welding processes were used to make tools and weapons, commonly known as blacksmiths. It is known that the Egyptians used forms of welding to make gold tools, jewelry, and decoration. During the 1800’s a new process was formed by using carbon electrodes to form an arc. This was done by Sir Humphrey Davy, which carried on to become Carbon Arc Welding and the most used process during the late 1800’s. As time evolved so did the
These globules act as a lubricant, decreasing the friction coefficient between the tools and the materials by creating discontinuities of chip fragmentation. Therefore, it reduces cutting force and then, the tool wear rate is minimized [13]. Different alloying elements help to improve the machinability are usually added to brass. The most common element used in this situation is lead, which improves the machinability with excellent chip breakage, low tool wear and high applicable cutting parameters. These aspects can be explained by two basic phenomena; in the first, the solubility of lead in brass is extremely low and lead segregates in the entire microstructure, particularly at the grain boundaries.
Something all young people consider is what they wish to do for the rest of their lives.
Fabrication at the factory utilizes a mix of robotics and manual labor to produce the body of the V-Rod. Robots that are designed to cut pipe are capable of completing a single operation within 3 seconds. Other fabrication robots utilize 1800 watt lasers that can perform cutting operations at the rate of 100 inches per minute. Where robotics can be used to perform high speed cutting and welding operations, skilled workers are a...
Pounding metal and fabricating metal in thin sheets and sections that humans need or want has a long history. The discovery of how to make and control fire made extracting metals form or more efficient instead of having to find almost pure nuggets of metal. In many civilizations copper was the metal they used but that was succeeded by bronze eventually it is made of copper and tin.
"Welding Processes, Welding Faults, Defects & Discontinuities For NDT Technicians Part 3." Hera.org. Hera, n.d. Web. 15 Mar. 2014. .
Arc welding and oxyfuel welding were among the first processes to disclose late in the years, and electric resistance welding followed early after. Welding technology progressive quickly during the late 20th century as the world wars drove the demand for the best joining methods. Following the wars, several welding techniques were improved, intercept manual methods likely SMAW, now one of the most popular welding methods, as well as semi-automatic and automatic-like processes such as GMAW, SAW, FCAW and ESW. Developments continued with the creation of laser beam welding, electron beam welding, magnetic pulse welding (MPW), and dissension stir welding in the later half of the hundred years. Today, the science last to advance robot welding is commonplace in business settings, and researchers retain to develop untried welding methods and gain greater understanding of weld
The creation of oxy fuel welding and development of the first torch where two French engineers Edmond Fouche and Charles Picard became the first engineers to create the first stages of
The metal’s hardness along with its great tensile strength and ability to withstand extremely high temperatures make it ideal for use in the filaments in incandescent light bulbs, cathode-ray tubes, X-ray tubes, vacuum tube filaments, and rocke...
There are number of methods to fabricate MEMS like silicon surface micromachining, silicon bulk machining, electro discharge machining, LIGA (in German, Lithographie, Galvanoformung(Electro Plating), Abformung(Injection Moulding)) .Only silicon surface micromachining is discussed here.
Welding was invented in the 1900s but lets go back a little to middle age that was when blacksmithing was the best method to use before welding. Now Edmund Davy of England was the one who discovered acetylene in 1836. Some of the others inventors were Auguste De Meritens who worked on how heating of an arc can join two pieces of metal, C.L. Coffin was one one who created a welding process with an electrode. There was other people that helped make welding more efficient. As the years past by welding was getting...
During the middle ages welding was very common. Early Egyptians learned the art of welding. Several of their tools were made by welding. A set of specialized workmen called blacksmiths created tools by melting the metal, then hammering them together. This method did not change much until the dawn of the 19th century which held major breakthroughs in welding. An open flame (acetylene) was very important to the history of welding. It allowed manufactures to make metal tools and equipment. In 1836 a man named Edmund Davy discovered acetylene which was soon utilized in the welding industries. Coated metal electrodes were first introduced in the 1900s. A coating of lime covered the electrode and made the weld much more stable. A number of other welding processes were also invented, such as seam welding, spot welding, flash butt welding, and projection welding. Stick welding also became popular around this time too. In the 1920s automatic welding was first introduced by P.O. Nobel. Automatic welding integrated the use of arc voltage and bare wire. It was mainly used for fixing old, molding metals. Several types of electrodes were also developed during this decade. A new type of welding was developed in the 1940s by Meredith. This became known as Heliarc Welding. Gas shielded arc welding or GTAW was another significant milestone in the welding history. Several advancements in the welding field were made in the 1960s. Dual shield, inner shield, and electro slag were some of the more important kinds developed. Plasma arc was also invented and was mainly used for metal spraying. Even now more techniques are being made. For example, laser welding was developed by the Russians and is being used more and more every day (“Welcome to
The Web. The Web. 28 Apr. 2014. The 'Standard' of the 'Standard'. Metal Melting 101 - How To.
In 1831, using his "induction ring", Faraday made one of his greatest discoveries - electromagnetic induction: the "induction" or generation of electricity in a wire by means of the electromagnetic effect of a current in another wire. The induction ring was the first electric transformer. In a second series of experiments in September he discovered magneto-electric induction: the production of a steady electric current. To do this, Faraday attached two wires through a sliding contact to a copper disc. By rotating the disc between the poles of a horseshoe magnet he obtained a continuous direct current. This was the first generator. From his experiments came devices that led to the modern electric motor, generator and transformer.